The present invention relates, in general, to electrical connectors and, more specifically, to radially resilient electrical sockets, also referred to as barrel terminals, in which a cylindrical electrical prong or pin is axially inserted into a socket whose interior surface is defined by a plurality of contact strips or wires which are bent into a hyperbolic, radially inward extending shape by angularly offset strip ends.
Radially resilient electrical sockets or barrel terminals are a well known type of electrical connector as shown in U.S. Pat. Nos. 4,657,335 and 4,734,063.
In such electrical sockets or barrel terminals, a generally rectangular stamping is formed with two transversely extending webs spaced inwardly from and parallel to opposite end edges of the sheet. Between the inner side edges of the transverse web, a plurality of uniformly spaced, parallel slots are formed to define a plurality of uniformly spaced, parallel, longitudinally extending strips which are joined at opposite ends to the inward side edges of both transverse webs. Other longitudinally extending slots are coaxially formed in the sheet and extend inwardly from the end edges of the blank to the outer side edges of the transverse webs to form a plurality of uniformly spaced, longitudinally extending tabs projecting outwardly from each transverse web.
The blank or sheet is then formed into a cylinder with the longitudinal strips extending parallel to the axis of the now cylindrical sheet. A closely fitting cylindrical sleeve is slipped coaxially around the outer periphery of the cylindrical blank, and extends axially substantially between the outer edges of the transverse webs. The mounting tabs at each end of the blank are then bent outwardly across end edges of the sleeve into radially extending relationship to the sleeve.
A relatively tight-fitting annular collar or outer barrel is then axially advanced against the radially projecting tabs at one end of the sleeve and slipped over the one end of the sleeve driving the tabs at that end of the sleeve downwardly into face-to-face engagement with the outer surface of the one end of the sleeve. The fit of the annular collar to the sleeve is chosen so that the end of the cylindrical blank at which the collar is located is fixedly clamped to the sleeve against both axial or rotary movement relative to the sleeve.
A tool typically having an annular array of uniformly spaced, axially projecting teeth is then engaged with the radially projecting tabs at the opposite end of the sleeve. The teeth on the tool are located to project axially between the radially projecting tabs closely adjacent to the outer surface of the cylindrical sleeve. The tool is then rotated about the longitudinal axis of the cylindrical sleeve while the sleeve is held stationary to rotatably displace the engaged tabs approximately 15xc2x0 to 45xc2x0 from their original rotative orientation relative to the sleeve and the bent over tabs at the opposite end of the sleeve. The tool is then withdrawn and a second annular collar or outer barrel is force fitted over the tabs and the sleeve to fixedly locate the opposite end of the blank in a rotatably offset position established by the tool.
When completed, such an electrical socket has longitudinal strips extending generally along a straight line between the angularly offset locations adjacent the opposite ends of the cylindrical sleeve. The internal envelope cooperatively defined by the longitudinal strips is a surface of revolution coaxial to the axis of the cylindrical sleeve having equal maximum radii at the points where the strips are joined to the respective webs and a somewhat smaller radius midway of the length of the strips. The minimum radius, midway between the opposite ends of the strips, is selected to be slightly less than the radius of a cylindrical connector pin which is to be inserted into the barrel socket so that the insertion of the pin requires the individual longitudinal strips to stretch slightly longitudinally to firmly frictionally grip the pin when it is seated within the barrel socket.
To put it another way, because of the angular offset orientation of the opposed ends of each of the strips, each strip is spaced from the inner wall of the sleeve in a radial direction progressively reaching a maximum radial spacing with respect to the outer sleeve midway between the ends of the sleeve.
Such a radially resilient electrical barrel socket provides an effective electrical connector which provides secure engagement with an insertable pin; while still enabling easy manual withdrawal or insertion of the pin relative to the socket. Such connectors also provide a large electrical contact area between the pin and the socket which enables such connectors to be employed in high current applications.
It is also known to construct such an electrical connector in a manner in which one of the collars is formed as an integral part or extension of a support member forming a part of the overall connector. The afore-described assembly process remains the same except that the separate collars at both ends of the socket are replaced by one collar at one end and a hollow, cylindrical extension of a connector which can be inserted into or otherwise electrically connected to an electrical device, such as a vehicle alternator, etc. The hollow cylindrical end of the support receives and holds the tabs at the first end of the sleeve tight against rotation while the opposing tabs are angularly rotated. A collar or end cap is then clamped over the rotated tabs to maintain such tabs in the rotated position.
Such radially resistant sockets are adapted for receiving generally cylindrical pins or terminals which are slid into the open end of the bore extending through the contact into forced engagement with the hyperbolically shaped contact grid contact strips. The pin displaces the hyperbolically shaped strips which generates a holding force to retain the pin in the socket or barrel terminal under a predetermined retention or pull-out force resistance.
Also known in the connector art are detent mechanisms employed on the pin and socket to increase the pull-out force resistance holding the pin in the socket. Such a detent mechanism typically employs a radially inward extending projection on one or more of the grid strips which engages an annular recess formed in the pin. This detent not only forms a detectable insertion stop for the pin into the electrical socket; but, also, increases the pull-out force resistance due to the mechanical and friction engagement between the grid contact projection(s) and the annular recess in the pin.
However, such detent mechanisms provide only a predetermined amount of pull-out force resistance. Certain electrical connector applications may desirably require increased pull-out force resistance magnitudes.
Thus, it would be desirable to provide an electrical connector employing a radially resistant electrical socket which has increased pull-out force resistance with minimal modification to the socket design. It would also be desirable to provide such an electrical connector in which the pull-out force resistance can be easily varied to suit various application requirements.
In one aspect of the present invention, an electrical connector is disclosed as including a radially resilient barrel socket having a bore with a first inner diameter extending from a first end. A stop member has a bore with a second inner diameter at least as large as the first diameter of the bore in the barrel socket. Means are provided for spacing the stop member from the one end of the barrel socket and defining a recess between the second inner diameter of the bore in the stop member and the one end of the barrel socket. The recess has a third inner diameter greater than the second inner diameter and the one end of the bore in the barrel socket. Means are provided for fixing the stop member and the spacing means with respect to the one end of the barrel socket. An electrically conductive member having an end pin is insertable through the fixing means, the spacing means and the stop member into the bore in the barrel socket. At least one projection is carried on the pin. The at least one projection is insertable through the inner diameter of a bore formed in the fixing means into the recess defined by the spacing means. An inner edge of the bore in the fixing means and an inner edge of the bore in the spacing means resisting movement of the at least one projection on the pin axially outward from the one end of the barrel socket up to a predetermined pull-out force.
In another aspect, the spacing means is a spacer member having a bore with the third inner diameter. The third inner diameter is larger than the second inner diameter of the stop member and the first inner diameter of the bore in the barrel socket. The recess is formed radially inward of the third inner diameter of the spacer member.
In another aspect, the fixing means includes an end cap having a sidewall and an end wall. A bore is formed in the end wall of an inner diameter sized to allow free passage of the at least one projection therethrough. An inner edge of the end wall surrounding the inner diameter of the bore is disposed adjacent to an inner edge of the spacing means surrounding the bore in the spacing means to resist axially outward flexure of the inner edge of the spacing means forces are exerted on the pin and the connector tending to move the pin is moved in an axially outward direction relative to the one end of the barrel socket. The end cap is preferably fixedly mounted on the barrel socket.
In one aspect, the at least one projection includes a single continuous, annular projection on the pin.
In another aspect, the spacing means has an inner edge surrounding the bore in the spacing means which is capable of axial flexure on insertion of the projection on the pin therethrough to allow passage of the projection into the recess. The fixing means and the spacing means resist flexure of the inner edge of the spacing means in an axial direction away from the one end of the barrel socket in a direction tending to separate the pin from the barrel socket.
The electrical connector according to the present invention uniquely provides different insertion or push-in force levels and pull-out force levels with the same connector structure. Without modification to an existing resilient barrel socket contact, the addition of a few additional components provides for a comparatively low push-in insertion force to trap a projection on an end pin portion of an electrically conductive end form in a recess formed at one end of the electrical connector. Pull-out movement of the projection and the end form from the barrel socket contact is resisted up to a comparatively high pull-out force level to resist separation of the conductive member from the connector body.
The inventive electrical connector employs a radially resilient electrical socket of many different configurations which is provided with a pull-out force resistance means to enable the pull-out force resistance of a pin insertable into the electrical socket to be increased to higher magnitudes as well as being able to be variably selected to suit different application requirements. This increased pull-out force resistance is achieved with few, if any, modifications to the electrical socket structure.